Automatic fire extinguisher



1945 o. E. BARNARD 2,405,125

AUTOMATIC FIRE EXTINGUiSHER Filed Sept. 11, 1945 ['5 Mai mvmrmnQRALEQBARNARD AWOHN EYS Patented Aug. 6, 1946 AUTGMATIC FIREEXTINGUISHER Oral E. Barnard, Montreal, Quebec, Canada, assignor toDominion Merchants Company Limited, St. Laurent, Quebec, CanadaApplication September 11, 1943, Serial No. 501,922

4 Claims.

This invention relates to automatic fire extinguishers and hasparticular reference to that type of fire extinguisher which is equippedwith an explosive head containing a powder charge which is exploded toblow out a portion of the head and thereby provide a discharge openingthrough which the fire extinguishing substance is discharged from itscontainer.

One objection to conventional fire extinguishers of the explosive head.type is that the exploded head must be scrapped and rep-laced by anentirely new head when the discharged container is turned in forre-charging. This is due to the fact that the wall of the powder chamberwhich is ruptured by explosion of the powder charge is cast integralwith the body portion of the head in such manner that the rupture ofsaid wall makes it impractical to repair the head for reuse and the onlyfeasible alternative is the substitution of an entirely new head.

Another objection to conventional fire extinguishers of the explosivehead type is that the explosive head is of intricate design and must beproduced by a die casting operation which makes it diflicult to avoidporosity of the casting at the thin critical section of the powderchamber wall which is ruptured by explosion of the powder charge. In theconventional die cast explosive the powder chamber wall which isruptured by the explosion constitutes a dividing wall between thepowderchamber and the interior of the container in which the fireextinguishing substance is contained. If the metal in this thin criticalwall section. is porous, leakage of the fire extin uishing substanceinto contact with the Y powder charge is apt to ensue, thus wetting thecharge and preventing its efficient explosion.

A further objection to the conventional explosive head is that thecontainer must be charged through a side opening in the head. This sideopening provides another possible point of leakage nd the machiningthereof constitutes a very complicated and expensive operation.

The purpose of the present invention is to provide an explosive head forfire extinguishers which is free of the foregoing objections and whichhas certain characteristic advantages not heretofore obtained in suchdevices. This purpose is accomplished by making the head in two partscomprising (1) a body portion of simplified design which may beeconomically produced by the sand casting method and (2) a blow-out plugassembly which may be machined out of solid bar stock. The body of thehead is provided with a cavity having a bottom opening which serves bothas a filling and discharge opening for the container to which the headis applied. The plug assembly includes a stem comprising a solid upperportion and a cored out lower portion which are integrally joinedtogether by a relatively thin frangible annular all section. This stemis arranged in the cavity of the head with the cored out lower portionof the stem screwed into and closing said opening. A sleeve is screwedonto the solid upper portion of the stem so that the lower face of thesleeve forms the upper wall of a pow der chamber whose outer side wallis formed by the circular wall of said cavity and whose remaining wallsare formed by portions of said stem. The lower portion of the stem iscored out to provide a downwardly facing bore or cavity which is closedat the top by the solid upper portion of the stem and the frangibleannular wall section which joins the two parts of the stem together.With this arrangement the explosion of the powder charge placed in thepowder chamber results in the rupture of the thin wall sectionconnecting the two parts of the stem and in the blowing out of the solidor upper part of the stem in such manner that the lower or cored outpart of the stem, including flange 29, is left in place within saidopening in the form of an open ended tube through which he contents ofthe container are discharged. This leaves the body of the head in anundamaged condition and when the fire exti. gu'sher is turned in forre-charging the portion of the head left in the combined filling anddischarge opening may be readily removed to permit application of a newplug assembly to said body after the container has been re-chargedthrough said opening.

Proceeding now to a more detailed description of this inventionreference will be had to the accompanying drawing, in which Fig. 1 is avertical sectional view of the body portion and plug assembly of anexplosive head made in accordance with the invention.

Fig. 2 is a side elevational view of the stem portion of the plugassembly as it appears per se.

The body portion and the blow-out plug assembly of my improved explosivehead are respectively indicated at 5 and 6. The body 5 is preferably aone-piece hollow sand casting provided with an internal transversepartition forming the bottom wall of an upper cavity 8 and the top wallof a lower cavity 9, said cavities communieating with each other througha combined filling and discharge opening ill provided in said partition.The body 5 is also provided with a later ally extending internallythreaded socket H in which the holder E2 of a powder igniting fuseelement l2a is screwed, said socket being in communication with thelower portion of cavity 8 through opening The lower wall portion It ofcavity 53 is internally threaded as indicated at in for engagement withthe usual threaded neck extension of a conventional container to whichthe head is applied, the container being charged and discharged throughthe opening Ill.

The plug assembly 6 comprises a stem iii and an associated sleeve I1.The stem is fabricated so that, in effect, it comprises a solidexternally threaded upper part I8 and a tubular externally threadedlower part I9, the latter being screwed into opening I and beingprovided, at its juncture with the upper part I8, with an outwardlydirected flange which overlies an annular bottom wall portion 2I ofcavity 8 surrounding opening I 0. The flange 20 and the annular wall 2Iare provided with relatively staggered annular sealing ribs 22a which,when the stem is screwed home, embed themselves in a sealing washer 23arranged beneath flange 20. The bore IIa of tubular stem portion I 9 isopen at its lower end and is closed at its upper end by the lowerextremity of the upper solid stem portion I8, the two parts of the stembeing integrally joined at the upper end of said bore by a thinfrangible wall section 24 whose upper surface forms with the uppersurface of flange 20 the bottom wall of a powder chamber 26, the topwall of which is formed by the lower surface of sleeve I! which isscrewed onto the upper stem portion I8. The outer and inner side wallsof powder chamber 25 are formed, respectively, by the circumferentialwall of cavity 8 and by that portion of stem section I8 which liesbetween sleeve I! and the upper surface of flange 20, it being notedthat the lower face of the sleeve is spaced an appreciable distanceabove said flange,

The inner circumferential Wall surface of cavity 8 is covered by a liner28 composed of fibrous or other suitable non-metallic material, thelower end of said liner terminating in an inwardly directed flange I7.This liner prevents direct contact between. the inner circumferentialwall of cavity 8 and the solder or other sealing substance 26a which isplaced in the outer portion of the cavity,

A charge of powder is trapped in powder chamber 26 as indicated and whenthis charge is ignited by the fuse element IZa it explodes and the forceof the explosion ruptures the thin wall 24 connecting the upper andlower stem parts I8 and I 9 and causes the upper part I8, together withthe sleeve I7, to be blown clear of cavity 8, the stem part I9 andflange 20 being left in place in the opening ID in the form of anopen-ended tube through which the contents of the container aredischarged. Since the frangible wall 24 is readily ruptured by the forceof the explosion no damage is caused to the body portion 5.Consequently, When the exploded container is turned in for rechargingthe screw threaded stem portion I9 may be readily removed from openingI0 to permit recharging of the container through said opening. A newplug assembly is then applied and the container is then ready forre-use.

It is important that flange 20 be left in place as a protective coveringfor the sealing washer surface 2| when the plug portion I8 is blown outsince said surface is easily damaged and may be ruined if left exposedwhen the container is turned in for re-charging.

Having thus described the preferred embodiment of my invention it willbe understood that various modifications may be resorted to within thescope and spirit of the invention as defined by the appended claims.

I claim:

1. An explosive head for fire extinguishers comprising a body portionand a separately formed 29 engaging the lower face of sleeve blow-outplug assembly fitted together with a portion of the plug assemblremovably inserted in and plugging an opening in the head through whichthe container with which the head is associated is charged anddischarged, the portion of the plug assembly inserted in said openingcomprising a lower tubular stem section whose bore is open at thecontainer end thereof and is closed at the opposite end by anothersection of the plug assembly to which the tubular section is integrallyjoined by a relatively thin and weak connecting wall, said body and plugassembly presenting chamber forming walls conjointly providing a powderchamber in which the explosion of a powder charge is effective torupture said relatively thin and weak connecting wall and to cause thesecond mentioned section of the plug assembly to be blown away from thetubular section, the latter being left in place in said opening in theform of a removable tubular section which is open at both ends to permitdischarge of the container contents therethrough.

2. An explosive head for fire extinguishers comprising a hollow bodyprovided with an internal transverse partition forming the bottom wallof an upper cavity and the top wall of a lower cavity, said cavitiesbeing in communication with each other through a combined filling anddischarge opening in said partition, a stem arranged in said uppercavity and comprising a tubular lower section having its upper endintegrally joined to a solid upper section by a relatively thin and weakconnecting wall, said tubular section of the stem being removablyinserted in said opening and the bore of said tubular section being openat one end to said lower cavity and being closed at the opposite end bythe solid upper section of the stem and by said relatively thin and weakconnecting wall, said stem and the circumferential wall of said uppercavity presenting chamber forming walls conjointly providing a powderchamber in which the explosion of a powder charge is effected to rupturesaid relatively thin and weak connecting wall and to blow the solidupper section of the stem out of said upper cavity, the lower tubularsection of the stem being left in place in said opening in the form of atube which is open at both ends to serve as a discharge outlet for thecontents of the container to which the head is applied.

3. An explosive head as set forth in claim 2, in which the said uppersection of the stem comprises a sleeve threaded on an integral stemportion, the said upper stem section being received in the said uppercavity and in which the outer side and top walls of said powder chamberare formed, respectively, by the circumferential wall of said uppercavity and by the lower face of said sleeve, the remaining walls of saidpowder chamber being formed by portions of said stem located immediatelyadjacent said relatively thin and weak connecting wall.

4. An explosive head as set forth in claim 2, in which the innercircumferential wall of said upper cavity is covered by a non-metallicliner which is interposed between said wall and said stem and which alsocovers portions of said wall lying above said stem, said liner servingto prevent fusion between said wall and sealing material placed in theupper end of said cavity above said stem,

ORAL E. BARNARD.

